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data-v-b3fd67f8><div class="item" role="button" tabindex="0" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><h2 class="text" data-v-b3fd67f8>HarmonyOS 开发准备</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-b3fd67f8><span class="vpi-chevron-right caret-icon" data-v-b3fd67f8></span></div></div><div class="items" data-v-b3fd67f8><!--[--><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/quickstart/%E9%B8%BF%E8%92%99%E6%93%8D%E4%BD%9C%E7%B3%BB%E7%BB%9F%E7%AE%80%E4%BB%8B.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>鸿蒙操作系统简介</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/quickstart/%E6%B3%A8%E5%86%8C%E6%88%90%E4%B8%BA%E5%BC%80%E5%8F%91%E8%80%85.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>注册成为开发者</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/quickstart/DevEco%20Studio%20%E9%9B%86%E6%88%90%E5%BC%80%E5%8F%91%E7%8E%AF%E5%A2%83.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>DevEco Studio集成开发环境</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/quickstart/%E6%9E%84%E5%BB%BA%E7%AC%AC%E4%B8%80%E4%B8%AAHarmonyOS%E5%BA%94%E7%94%A8.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>构建第一个HarmonyOS应用</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="no-transition group" data-v-c40bc020><section class="VPSidebarItem level-0 collapsible collapsed has-active" data-v-c40bc020 data-v-b3fd67f8><div class="item" role="button" tabindex="0" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><h2 class="text" data-v-b3fd67f8>ArkTS 编程语言</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-b3fd67f8><span class="vpi-chevron-right caret-icon" data-v-b3fd67f8></span></div></div><div class="items" data-v-b3fd67f8><!--[--><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/Index.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>简介</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E5%9F%BA%E7%A1%80%E8%AF%AD%E6%B3%95.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>基本语法</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E5%87%BD%E6%95%B0.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>函数</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E9%9D%A2%E5%90%91%E5%AF%B9%E8%B1%A1.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>面向对象</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E6%B3%9B%E5%9E%8B.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>泛型</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E7%A9%BA%E5%AE%89%E5%85%A8.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>空安全</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E6%A8%A1%E5%9D%97%E4%B8%8E%E5%91%BD%E5%90%8D%E7%A9%BA%E9%97%B4.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>模块与命名空间</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E5%BC%82%E6%AD%A5%E5%B9%B6%E5%8F%91.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>异步并发</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter1/%E5%A4%9A%E7%BA%BF%E7%A8%8B%E5%B9%B6%E5%8F%91.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>多线程并发</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="no-transition group" data-v-c40bc020><section class="VPSidebarItem level-0 collapsible collapsed" data-v-c40bc020 data-v-b3fd67f8><div class="item" role="button" tabindex="0" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><h2 class="text" data-v-b3fd67f8>ArkUI 方舟UI框架</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-b3fd67f8><span class="vpi-chevron-right caret-icon" data-v-b3fd67f8></span></div></div><div class="items" data-v-b3fd67f8><!--[--><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/Index.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>简介</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/ArkTS%E5%A3%B0%E6%98%8E%E5%BC%8FUI%E5%9F%BA%E6%9C%AC%E8%AF%AD%E6%B3%95.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>基本语法</p><!--]--></a><!----></div><!----></div><section class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" tabindex="0" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E7%9B%92%E5%AD%90%E6%A8%A1%E5%9E%8B.html" data-v-b3fd67f8><!--[--><h3 class="text" data-v-b3fd67f8>通用属性</h3><!--]--></a><!----></div><div class="items" data-v-b3fd67f8><!--[--><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E7%9B%92%E5%AD%90%E6%A8%A1%E5%9E%8B.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>盒子模型</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E6%96%87%E6%9C%AC%E5%B1%9E%E6%80%A7.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>文本样式</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E4%BD%8D%E7%BD%AE%E8%AE%BE%E7%BD%AE.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>位置设置</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E8%83%8C%E6%99%AF%E8%AE%BE%E7%BD%AE.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>背景设置</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E5%BD%A2%E7%8A%B6%E8%AE%BE%E7%BD%AE.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>形状设置</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E6%98%BE%E9%9A%90%E8%AE%BE%E7%BD%AE.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>显隐设置</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-2 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/%E9%80%9A%E7%94%A8%E5%B1%9E%E6%80%A7/%E8%A7%86%E6%95%88%E8%AE%BE%E7%BD%AE.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>视效设置</p><!--]--></a><!----></div><!----></div><!--]--></div></section><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/Stack%E5%B1%82%E5%8F%A0%E5%B8%83%E5%B1%80.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>Stack 层叠布局</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/RealtiveContainer%E7%9B%B8%E5%AF%B9%E5%B8%83%E5%B1%80.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>RealtiveContainer 相对布局</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-b3fd67f8 data-v-b3fd67f8><div class="item" data-v-b3fd67f8><div class="indicator" data-v-b3fd67f8></div><a class="VPLink link link" href="/chapter2/RealtiveContainer%E7%9B%B8%E5%AF%B9%E5%B8%83%E5%B1%80.html" data-v-b3fd67f8><!--[--><p class="text" data-v-b3fd67f8>相抵</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-5d98c3a5 data-v-1428d186><div class="VPDoc has-sidebar has-aside" data-v-1428d186 data-v-39a288b8><!--[--><!--]--><div class="container" data-v-39a288b8><div class="aside" data-v-39a288b8><div class="aside-curtain" data-v-39a288b8></div><div class="aside-container" data-v-39a288b8><div class="aside-content" data-v-39a288b8><div class="VPDocAside" data-v-39a288b8 data-v-3f215769><!--[--><!--]--><!--[--><!--]--><nav aria-labelledby="doc-outline-aria-label" class="VPDocAsideOutline" data-v-3f215769 data-v-a5bbad30><div class="content" data-v-a5bbad30><div class="outline-marker" data-v-a5bbad30></div><div aria-level="2" class="outline-title" id="doc-outline-aria-label" role="heading" data-v-a5bbad30>本页目录</div><ul class="VPDocOutlineItem root" data-v-a5bbad30 data-v-b933a997><!--[--><!--]--></ul></div></nav><!--[--><!--]--><div class="spacer" data-v-3f215769></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-39a288b8><div class="content-container" data-v-39a288b8><!--[--><!--]--><main class="main" data-v-39a288b8><div style="position:relative;" class="vp-doc _chapter1_%E5%BC%82%E6%AD%A5%E5%B9%B6%E5%8F%91" data-v-39a288b8><div><h1 id="异步编程" tabindex="-1">异步编程 <a class="header-anchor" href="#异步编程" aria-label="Permalink to &quot;异步编程&quot;">​</a></h1><h2 id="基本概念" tabindex="-1">基本概念 <a class="header-anchor" href="#基本概念" aria-label="Permalink to &quot;基本概念&quot;">​</a></h2><p>任务是完成某项操作要执行的一段代码，一个任务可以执行任何特定操作的代码，可能是简单的打印语句、复杂的算法处理、网络请求或 I/O 操作等。这些任务的执行时间各不相同，打印语句执行时间通常很短，而网络请求和 I/O 操作可能耗时较长。</p><p>如果所有的任务按照顺序执行，耗时较长的任务可能会阻塞线程，导致整体性能下降，进而影响用户体验。为了更高效地管理和执行这些任务，<code>JavaScript</code> 将要执行的任务分为同步任务和异步任务使得<code>JavaScript</code> 能够在单线程环境中有效地处理耗时操作，而不阻塞主线程。</p><ul><li>同步任务：这些是立即执行的任务，不需要等待任何条件或事件，会阻塞后续代码的执行。</li><li>异步任务：这些任务不会立即执行，而是先挂起，被推迟到未来某个时间点执行，不会阻塞后续代码的执行。</li></ul><p>在 ES6（ECMAScript 2015，JavaScript标准规范） 之前，<code>JavaScript</code> 的异步任务主要是通过如 <code>setTimeout</code>, <code>setInterval</code>来实现。</p><p>示例代码</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//同步代码</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Start&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//异步任务</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;异步任务1&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//异步任务</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;异步任务2&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">setInterval</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(()</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">{</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">     console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;异步任务3&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1000</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//同步代码</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;End&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span></code></pre></div><p>输出结果</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">Start</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">End</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">异步任务1</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">异步任务2</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">异步任务3  （</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 秒后开始循环输出）</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">异步任务3  （再次循环输出）</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">异步任务3  （继续每秒输出）</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">...</span></span></code></pre></div><p>分析执行流程</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Start&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">); 和 console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;End&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">); 是同步代码，立即执行。</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> setTimeout 的回调虽然是 </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 毫秒延迟，但它们是异步任务，会等到当前同步任务执行完后再执行。</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> setInterval 会每隔 </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 秒重复执行其回调，每次执行都是一个新的宏任务。</span></span></code></pre></div><h2 id="事件循环" tabindex="-1">事件循环 <a class="header-anchor" href="#事件循环" aria-label="Permalink to &quot;事件循环&quot;">​</a></h2><p>异步任务之所以能够被推迟到未来的某个时间点执行，而不阻塞主线程，主要依赖于<strong>事件循环机制</strong>和<strong>任务队列</strong>来实现的。</p><ul><li>事件循环机制：是一种调度异步任务的模型。</li><li>任务队列：任务队列是用来存储异步任务的容器，等待后续某个时间点，被事件循环调度。</li></ul><p>下图展示了<code>JavaScript</code>执行引擎启动后，各个任务的执行流程。</p><p><img src="/assets/1736920753457-9dd9c236-6d20-41cd-9654-0824a6bc4828.D9_2RFGb.png" alt=""></p><p>在 ES6 之前（ECMAScript 2015，<code>JavaScript</code>标准规范），所有异步任务都被放在同一个任务队列中，缺乏更精细的控制，所以从ES6开始引入了宏任务和微任务对异步任务进行更精细的控制。</p><h2 id="宏任务和微任务" tabindex="-1">宏任务和微任务 <a class="header-anchor" href="#宏任务和微任务" aria-label="Permalink to &quot;宏任务和微任务&quot;">​</a></h2><p>从ES6开始引入了大量的新特性（包括 <code>Promise</code> 和 微任务），引入微任务是为了优化任务调度，减少延迟，提高性能，可以更高效地处理一些高优先级的小任务。</p><ul><li>微任务：具有高优先级的异步任务，通常用于较短时间内的异步操作，如 <code>Promise</code> 等操作。</li><li>宏任务：具有较低优先级的异步任务，通常用于延迟执行或需要等待的操作，如 <code>setTimeout</code> 等操作。</li></ul><p>这种任务划分和管理机制使得 <code>JavaScript</code> 能够在单线程环境中有效地处理异步任务，提升程序的响应性和用户体验。</p><p>JavaScript 执行引擎通过事件循环机制、宏任务队列、微任务队列在管理并执行异步任务，</p><p><img src="/assets/1736906026083-d1afe1ba-8b0b-40e4-85a3-0aecc166061d.BTh6XgXZ.png" alt=""></p><p>解释：</p><ol><li><code>JavaScript</code> 执行引擎启动后，开启一条主线程，按照代码顺序依次往下执行；</li><li>当执行到宏任务时，将宏任务添加到宏任务队列，等待后续事件循环调度，JavaScript主线程继续往下执行；</li><li>当执行到微任务时，将微任务添加到微任务队列，等待后续事件循环调度，JavaScript主线程继续往下执行，直到所有同步代码执行完毕；</li><li>执行完所有同步代码之后，启动事件循环，先依次执行完微任务队列中所有的微任务，直到微任务微空。</li><li>再执行一个宏任务后，判断微任务队列是否为空（因为可能有新的微任务加入到微任务队列）</li><li>如果微任务队列不为空，则继续执行微任务队列中的所有微任务，如此循环。</li></ol><p>示例代码</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//同步代码</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Start&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//宏任务: 该回调函数的任务会被添加到宏任务队列</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;宏任务1&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;宏任务2&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//微任务</span></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">().</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;微任务1&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//微任务</span></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">().</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;微任务2&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//同步代码</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;End&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span></code></pre></div><p>执行结果</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">Start</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">End</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">微任务1</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">微任务2</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">宏任务1</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">宏任务2</span></span></code></pre></div><p>执行流程分析</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 先执行同步代码，</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">输出</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">: Start 和 End。</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() 创建的宏任务回调被加入 宏任务队列。</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">().</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() 创建的微任务回调被加入 微任务队列。</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 同步代码执行完后，开启事件循环，会执行完微任务队列中所有的微任务，</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">输出</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">: 微任务1、 微任务2</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">-</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 执行完微任务后，事件循环会从宏任务队列中取出任务执行，</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">输出</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">: 宏任务1、宏任务2</span></span></code></pre></div><p>好了👌，异步任务的执行原理你搞清楚了吗？接下来我们学习使用<code>Promise</code>创建异步任务，并处理异步任务的结果。</p><h2 id="promise-处理异步任务" tabindex="-1">Promise 处理异步任务 <a class="header-anchor" href="#promise-处理异步任务" aria-label="Permalink to &quot;Promise 处理异步任务&quot;">​</a></h2><p>异步任务（如网络请求、文件读写等）的耗时无法预知，因此无法直接在其执行过程中处理后续逻辑。为避免阻塞，我们需要一种机制，在任务完成后自动触发预设的成功/失败处理逻辑。开发者需提前定义这些处理逻辑，程序才能根据结果执行相应操作。 <strong><code>Promise</code> 是 <code>JavaScript</code> 中用于处理异步操作的对象</strong>。</p><p><code>Promise</code>它表示一个尚未完成但未来会完成的操作，并提供标准化的方式来处理成功或失败的逻辑。<code>Promise</code> 有三种状态：<code>pending</code>（进行中）、<code>fulfilled</code>（已成功）和 <code>rejected</code>（已失败），<code>Promise</code>对象创建后处于<code>pending</code>状态，异步操作完成后，根据成功或失败转换为<code>fulfilled</code>或<code>rejected</code>状态。</p><h3 id="基本用法" tabindex="-1">基本用法 <a class="header-anchor" href="#基本用法" aria-label="Permalink to &quot;基本用法&quot;">​</a></h3><p><code>Promise</code>最基本的用法是通过构造函数实例化一个<code>Promise</code>对象，传入一个带有两个参数的函数，称为<code>executor</code>函数。<code>executor</code>函数接收两个参数：<code>resolve</code>和<code>reject</code>，分别表示异步操作成功和失败时的回调函数。</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 1. 创建Promise（泛型声明结果类型）</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">结果类型</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt;((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">    // 异步操作（如网络请求、定时器等）</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    if</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (操作成功) {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">        resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(成功结果);  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// ✅ 触发 then()</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">        reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(失败原因);   </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// ❌ 触发 catch()</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 2. 处理结果</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> 结果类型</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">    // 成功逻辑</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}).</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">    // 失败逻辑</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span></code></pre></div><p>示例：以下代码创建了一个<code>Promise</code>对象并模拟了一个异步操作：</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> promise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">number</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Function</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Function</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">  //模拟耗时操作，3秒钟后，根据随机数的结果，处理成功或者失败的逻辑</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">  setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> num</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> number</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">();</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    if</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&gt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0.5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">      resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(num); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//成功，执行resolve函数</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">      reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Random number is too small&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">));  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//失败，执行reject函数</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  }, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">2000</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> number</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">`Promise resolved with result: ${</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">result</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">}`</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}).</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">`Promise rejected with error: ${</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">error</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">.</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">message</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">}`</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span></code></pre></div><p>两次执行结果分别如下：</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> rejected </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">with</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">: Random number is too small</span></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> resolved </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">with</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> result</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">: </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0.550281874674772</span></span></code></pre></div><h3 id="链式调用" tabindex="-1">链式调用 <a class="header-anchor" href="#链式调用" aria-label="Permalink to &quot;链式调用&quot;">​</a></h3><p>当你调用<code>then()</code>或者<code>catch()</code> 方法时，你可以传入一个回调函数，这个回调函数会在 <code>Promise</code> 状态变为 <code>fulfilled</code>或者<code>reject</code> 时执行。</p><p>这个回调函数可以返回一个普通值，也可以返回一个新的 <code>Promise</code>。</p><ul><li>如果回调函数返回一个普通值，该值会被包装成一个 <code>fulfilled</code> 状态的 <code>Promise</code>，并传递到下一个 <code>then() </code>方法中。</li><li>如果回调函数返回一个 <code>Promise</code> 对象，那么下一个<code>then()</code>将会等待这个新的 <code>Promise</code> 完成后再继续执行。</li></ul><p>这使得你可以链式处理异步操作，并且<code> then()</code> 方法始终返回一个新的 <code>Promise</code>，从而可以继续使用<code>.then()</code>进行链式调用。</p><p>示例 1：回调函数返回一个普通值</p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt;((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">  resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Hello&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);  </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  return</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> result </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">+</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot; World&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise1.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result);  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//Hello World</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span></code></pre></div><p>示例2：回调函数返回一个 <code>Promise</code></p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">    resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Hello&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result);  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 输出 &quot;Hello&quot;</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    return</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">        setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">            resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">+</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> &quot; World&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">        }, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1000</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    });  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 返回一个新的 Promise</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result);  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 输出 &quot;Hello World&quot;（等待 1 秒）</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span></code></pre></div><h3 id="异常捕获" tabindex="-1">异常捕获 <a class="header-anchor" href="#异常捕获" aria-label="Permalink to &quot;异常捕获&quot;">​</a></h3><p>你可以在链式调用中使用 <code>.catch()</code> 来捕获和处理任何一步操作中的错误。即使在链中的某个<code>.then()</code>发生了错误，错误会被传递到<code> .catch()</code> 中。</p><p><strong>触发<code>catch()</code>有以下几种情况：</strong></p><ul><li><p>当<code>Promise</code>处于<code>pending</code>状态时，调用 <code>reject()</code>或者<code>throw</code>抛出异常，会触发<code>catch()</code>。</p></li><li><p>当<code>Promise</code>处于<code>fulfilled</code>状态时，<code>throw</code>抛出异常或者返回一个拒绝的<code>Promise</code>，会触发 <code>catch()</code>。</p></li></ul><p><strong>示例1：当<code>Promise</code>处于<code>pending</code>状态时，<code>throw</code>抛出异常，触发<code>catch</code></strong></p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> promise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">number</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Function</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Function</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//模拟耗时操作，3秒钟后，根据随机数的结果，处理成功或者失败的逻辑</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> num</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> number</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">();</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&gt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0.5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">  resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(num); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//成功，执行resolve函数</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">  //reject(new Error(&#39;Random number is too small&#39;));</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">  //失败，执行reject函数</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  throw</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Random number is too small&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> number</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Success:&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, result)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}).</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">{</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Error:&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, error.message)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span></code></pre></div><div class="caution custom-block github-alert"><p class="custom-block-title">CAUTION</p><p></p><p>如果在<code>pending</code>状态执行异步操作，此时<code>throw</code>抛出异常，不能被<code>catch</code>捕获。要想被<code>catch</code>捕获建议使用<code>reject</code>传递错误数据。</p></div><p><strong>示例2：当<code>Promise</code>处于<code>fulfilled</code>状态时，<code>throw</code>抛出异常，触发<code>catch</code></strong></p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt;((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Success&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//输出：Success</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">throw</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;出错了...&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}).</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Error message&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,error.message); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 输出：出错了。。。</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span></code></pre></div><p><strong>示例3：当<code>Promise</code>处于<code>fulfilled</code>状态时，返回一个被拒绝的<code>Promise</code>，触发<code>catch</code></strong></p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt;((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">  resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Success&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//Success</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  return</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt;((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">    reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;失败了&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">))</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  })</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}).</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Error message&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,error.message);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">});</span></span></code></pre></div><h3 id="快速创建promise" tabindex="-1">快速创建Promise <a class="header-anchor" href="#快速创建promise" aria-label="Permalink to &quot;快速创建Promise&quot;">​</a></h3><p><strong>1. 方法作用</strong></p><ul><li><code>Promise.resolve(value)</code>：直接返回一个 <strong>已成功（fulfilled）</strong> 的 Promise 对象。</li><li><code>Promise.reject(reason)</code>：直接返回一个 <strong>已拒绝（rejected）</strong> 的 Promise 对象。</li></ul><p><strong>2. 使用场景</strong></p><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//1. 成功的Promise</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> successPromise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Hello World&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">successPromise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">res</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(res); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//输出：Hello World</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span>
<span class="line"></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//2. 失败的Promise</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> errorPromise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;aaa&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">errorPromise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&#39;Error message&#39;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, error.message); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//输出：abc</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span></code></pre></div><h3 id="其他静态方法" tabindex="-1">其他静态方法 <a class="header-anchor" href="#其他静态方法" aria-label="Permalink to &quot;其他静态方法&quot;">​</a></h3><p>除了 <code>Promise.resolve()</code> 和 <code>Promise.reject()</code>，Promise 还提供了几个强大的静态方法，用于处理多个异步任务或复杂逻辑。以下是它们的核心用法和适用场景：</p><h4 id="_1-promise-all-——-等待所有-promise-完成" tabindex="-1">1. <code>Promise.all()</code> —— 等待所有 Promise 完成 <a class="header-anchor" href="#_1-promise-all-——-等待所有-promise-完成" aria-label="Permalink to &quot;1. `Promise.all()` —— 等待所有 Promise 完成&quot;">​</a></h4><ul><li><strong>作用</strong>：并行执行多个 <code>Promise</code>，全部成功时返回结果数组任意一个失败则立即终止。</li><li><strong>适用场景</strong>：多个独立异步任务需全部完成（如并发请求多个接口）。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">2</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p3</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">3</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">); </span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">all</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">([p1, p2, p3])</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">results</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> number</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">[]) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(results.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">toString</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">())) </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// [1, 2, 3]</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(error.message)); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 任意一个失败时触发</span></span></code></pre></div><h4 id="_2-promise-race-——-取最快完成的-promise" tabindex="-1">2. <code>Promise.race()</code> —— 取最快完成的 Promise <a class="header-anchor" href="#_2-promise-race-——-取最快完成的-promise" aria-label="Permalink to &quot;2. `Promise.race()` —— 取最快完成的 Promise&quot;">​</a></h4><ul><li><strong>作用</strong>：返回第一个完成（无论成功或失败） 的 <code>Promise</code> 结果。</li><li><strong>适用场景</strong>：超时控制、竞速请求（如从多个 CDN 源加载资源）。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">resolve</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Winner&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">), </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">500</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">));</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> new</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">_</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> setTimeout</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Timeout&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)), </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1000</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">));</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">race</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">([p1, p2])</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result))  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// &quot;Winner&quot;（p1 更快）</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">error</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(error.message));</span></span></code></pre></div><h4 id="" tabindex="-1"><a class="header-anchor" href="#" aria-label="Permalink to &quot;&quot;">​</a></h4><h4 id="_3-promise-any-——-取第一个成功的-promise" tabindex="-1">3. <code>Promise.any()</code> —— 取第一个成功的 Promise <a class="header-anchor" href="#_3-promise-any-——-取第一个成功的-promise" aria-label="Permalink to &quot;3. `Promise.any()` —— 取第一个成功的 Promise&quot;">​</a></h4><ul><li><strong>作用</strong>：返回 第一个成功 的 <code>Promise</code> 结果，全部失败时才触发 <code>catch</code>。</li><li>应用场景：冗余请求（如多个备用 API 源，取最快可用的）。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Error 1&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">resolve</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Success&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> p3</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Error 2&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">any</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">([p1, p2, p3])</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result))  </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// &quot;Success&quot;（第一个成功的）</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  .</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">errors</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(errors.message)); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 全部失败时触发（AggregateError）</span></span></code></pre></div><blockquote><p><strong>特点</strong>： ✅ 忽略失败，只关注第一个成功结果 ❌ 全部失败时返回 <code>AggregateError</code>（包含所有错误原因）</p></blockquote><h2 id="await-sync" tabindex="-1">await/sync <a class="header-anchor" href="#await-sync" aria-label="Permalink to &quot;await/sync&quot;">​</a></h2><p><code>async/await</code>是用于处理异步操作的<code>Promise</code>语法糖，使编写异步代码更加简单和易读。使用<code>async</code>关键字声明异步函数，并使用<code>await</code>关键字等待<code>Promise</code>的解析（完成或拒绝），以同步方式编写异步操作的代码。</p><h3 id="async-函数声明" tabindex="-1"><code>async</code> 函数声明 <a class="header-anchor" href="#async-函数声明" aria-label="Permalink to &quot;`async` 函数声明&quot;">​</a></h3><ul><li>函数前加 <code>async</code> 关键字，表示该函数包含异步操作，无论函数内返回什么，都会被包装成 Promise返回。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">async</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> function</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetchData</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(){</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  return</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> &#39;Hello World&#39;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">	// 等价于 Promise.resolve(&quot;data&quot;)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> promise</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetchData</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">()</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">promise.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">{</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;成功&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,result)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span></code></pre></div><h3 id="await-等待-promise-完成" tabindex="-1"><code>await</code> 等待 Promise 完成 <a class="header-anchor" href="#await-等待-promise-完成" aria-label="Permalink to &quot;`await` 等待 Promise 完成&quot;">​</a></h3><ul><li><code>await</code> 只能在 <code>async</code> 函数内部使用。它会暂停代码执行，直到 <code>Promise</code> 变为 <code>fulfilled</code> 或 <code>rejected</code>。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">async</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> function</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">url</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;模拟网络请求中...&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  return</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> &quot;{&#39;name&#39;: &#39;zhangsan&#39;, &#39;age&#39;: 20}&quot;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">async</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> function</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> getUser</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">()</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&lt;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">&gt; {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> user</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> await</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;/api/user&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 等待 Promise 完成</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;用户信息：&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, user)</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  return</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> user</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">getUser</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">().</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">then</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">((</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">result</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=&gt;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">{</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(result)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">})</span></span></code></pre></div><div class="warning custom-block github-alert"><p class="custom-block-title">WARNING</p><p></p><p><code>await</code> 会阻塞代码，导致多个异步操作串行执行。可以使用 <code>Promise.all()</code> 让多个异步任务<strong>并行执行</strong>。</p></div><h3 id="try-catch-处理异常" tabindex="-1"><code> try/catch</code> 处理异常 <a class="header-anchor" href="#try-catch-处理异常" aria-label="Permalink to &quot;` try/catch` 处理异常&quot;">​</a></h3><ul><li>用 <code>try/catch</code> 捕获 <code>await</code> 后的 Promise 失败。</li></ul><div class="language-ts vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">ts</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">async</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> function</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">url</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">:</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> string</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  let</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> randomNumber </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">()</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  if</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (randomNumber </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&gt;=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0.5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    return</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> &quot;{&#39;name&#39;:&#39;张三&#39;, &#39;age&#39;:30}&quot;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> //等价于：Promise.resolve(...)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> Promise</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">reject</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;请求失败&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">)</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">async</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> function</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> loadData</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">  try</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">    const</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> data</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> await</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> fetch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;/api/data&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);	</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//如果fetch返回拒绝的Promise则，会触发catch</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">log</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(data); </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (error) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">    console.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">error</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Error messaage&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, error); </span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// 捕获 fetch 或 json() 的错误</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">  }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">//调用loadData</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">loadData</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">()</span></span></code></pre></div><div class="warning custom-block github-alert"><p class="custom-block-title">WARNING</p><p></p><p>如果不使用 <code>try/catch</code>，错误会传递到调用方的 <code>.catch()</code>。</p></div></div></div></main><footer class="VPDocFooter" data-v-39a288b8 data-v-e257564d><!--[--><!--]--><!----><nav class="prev-next" aria-labelledby="doc-footer-aria-label" data-v-e257564d><span class="visually-hidden" id="doc-footer-aria-label" data-v-e257564d>Pager</span><div class="pager" data-v-e257564d><a class="VPLink link pager-link prev" href="/chapter1/%E6%A8%A1%E5%9D%97%E4%B8%8E%E5%91%BD%E5%90%8D%E7%A9%BA%E9%97%B4.html" data-v-e257564d><!--[--><span class="desc" data-v-e257564d>Previous page</span><span class="title" data-v-e257564d>模块与命名空间</span><!--]--></a></div><div class="pager" data-v-e257564d><a class="VPLink link pager-link next" href="/chapter1/%E5%A4%9A%E7%BA%BF%E7%A8%8B%E5%B9%B6%E5%8F%91.html" data-v-e257564d><!--[--><span class="desc" data-v-e257564d>Next page</span><span class="title" data-v-e257564d>多线程并发</span><!--]--></a></div></nav></footer><!--[--><!--]--></div></div></div><!--[--><!--]--></div></div><footer class="VPFooter has-sidebar" data-v-5d98c3a5 data-v-e315a0ad><div class="container" data-v-e315a0ad><p class="message" data-v-e315a0ad>鸿蒙应用开发基础教程</p><p class="copyright" data-v-e315a0ad>Copyright © 2025-至今 wangqi</p></div></footer><!--[--><!--]--></div></div>
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